Electrolytio extraction of light metals contained in alloys



May 23. 1933-. HUUN 1,910,017

ELECTRCLY'IIQ EXTRACTION OF LIGHT METALS CONTAINED IN ALLOYS Filed Dec. 14, 1928 2' Sheets-Sheet l P4? AM,

May 23, 1933. p HUUN 1,910,017

ELECTROLYTIC EXTRACTION OF LIGHT METALS CONTAINED IN ALLOYS Filed Dec. 14, 1928 2 Sheets-Sheet 2 Fig.2.

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Patented May 23, 1933 UNITED STATES PATENT OFFICE PAUL LEON HULIN, OF GRENOBLE, FRANCE, ASSIGNOR T0 COMPAGl-NIE DE PRODUITS (THIMIQUES ET ELECTROMETALLURGIQUES PARIS, FRANCE ALAIS, FROGES ET CAMARGUE, OF

ELECTROLYTIC EXTRACTION OF LIGHT METALS CONTAINED IN ALLOYS Application filed' December 14, 1928, Serial No. 325,974, and in France December 21, 1927.

For extracting by electrolysis, from molten substances, alight metal contained in a denser alloy acting as anode, a classical device is known, in which are superposed, in a vat, three molten layers:

The anode, constituted by the dense melted alloy, lying at the bottom and covered by the electrolyte;

The bath or molten electrolyte, of intermediate density, lying between the anode and the cathode;

The cathode, made of light metal released by the electrolyte, floating as a liquid layer or sheet on the bat-h which ,it entirely covers.

In this device, the cathode and the anode being in a liquid condition, come in contact, each at its'own level, with the side wall of the vat. A short circuit thus exists between both electrodes, through the medium of this wall, and this accident is not uncommon. It is therefore necessary to constitute the said wall in such a manner as to prevent the direct passage of the current through the wall. Now, the latter must also be such that it cannot be disintegrated by the electrolyte.

These conditions present inconsistencies and difliculties of realization which are well known and for overcoming the same various solutions have been proposed.

The present invention has for object to re,- move the difficulties met with in carrying out the above mentioned classical device.

It is based on the utilization of the principle known in a quite different application according to which the cathode is progressively lifted above the bath and draws along with it the metal which agglomerates thereon in proportion as it is formed, by constituting a solidified rod adhering to the cathode.

The invention is therefore essentially characterized by the combination with a molten anode, which freely extends to the bottom of the electrolysis vat, of a cathode arranged opposite and above the same, and which is prevented from extending to the vat and held out of contact and at a suitable distance from the wall owing to the continuous lifting of the glomerated condition in the form of a rod circuit is avoided as well as any-adherence,

by contact between the cathode and other difliculties.

The side inner wall of the vat can then be lined with a coating of agglomerated carbon, which is the only material known as being capable of suitably resisting in certain baths of melted salts, mainly in those containing alkaline or alkali-earth fluorides.

The invention applies as well to the refining of light metals as to their extraction when they have been produced in the state of alloys.

The invention is carried out by means of a suitable plant the arrangements and essential elements of which are diagrammatically illustrated, by way of example only, in the accompanying drawings, Figure 1 and F igure 2.

The system comprises: a metal vat A, made and the wall,

of iron or steel, having a shape variable at vat. The hearth C, which may be plane or of bowl shape, is made of carbon; it is isolated from the vat and is anodically connected to the electrolytic circuit by a conductor 0. The anode-alloy covers the bottom where it forms a molten layer 1).

The molten electrolyte is situated immediately above at E.

The cathode is first formed of a metal cylinder F, usually of copper or bronze or similar alloy of good conductibility. It is hung from a metal rod of thesame nature f f, freely passing in guides G G and carried by a suspension having a vertical movement of great amplitude, such for instance as a screw a and its toothed nut 12, actuated by a worm e.

By means of this suspension, the cathode can be raised, at a reduced .and exactly adjusted speed, and have a vertical movement of rather great amplitude. Reversely', it can be lowered at will according to requirements and, in any case, after each operation.

The cathodic current is transmitted there- 5 to through the rod f, either by passing through the guides G G, formin or having a sliding contact, or through a exible conductor, or in any suitable manner.

The anode-alloy D is composed-of the light .metal to'be extracted, incorporated with a heavy metal, much less electro-positive, such for instance as magnesium-lead for extracting magnesium therefrom, or aluminiumcopper for extractin aluminium therefrom, or glucinum-copper or extracting glucinum therefrom, or other similar alloy, for extracting other light metals therefrom.

The electrolyte comprises, either alone, or in admixture in the necessary proportion with other suitable substances, one or more halogenated compounds, chloride or fluoride, of the light metal to be extracted, the suitable composition, in each case, being either known or easy to determine and does not form a part of the invention. It is to be noted that the density of the bath must be sufficiently high for preventing the light metal, which has been deposited under the cathode, from becoming detached and from going down again and that themelting point of the said metal must not be high enough to form and include, in the cathodic deposit, solidified portions of the bath preventing the operation, but this melting point must be, as far as possible, equal or preferably inferior to the melting point of the light metal which begins to form.

The operation of the new system is as follows: 1

The bath and the alloy-anode, to be treated, being brought .to molten condition by 'the usual means, the cylinder F is lowered in order to be in contact with the bath without being immersed therein. The electrolysis current is fed to the apparatus and a layer of fluid light metal 72, h is formed before long under the cathodic cylinder, which metal sometimes overflows about the cylinder, adheres thereto and begins to solidify.

\ From this moment, by applying to the new combination alloy-anode-bath-contacted cathode, the process known underthe name of rising contact cathode, the cathode F is slowly raised, according to'the well known method, at a speed which is controlled by observing the two opposed conditions which consist, on the one hand, in not breaking the contact between the bath and the cathode and, on the other hand, in not allowing the latter to unduly expand or to abandon metal in a separated condition.

On the lower face of the cathode is thus obtained a deposit of light metal, first fluid and pasty, which solidifies and, by re-forming it- 65 self in the same way and replacing at k h the cylinder F in proportion as the latter rises by drawing along the successive layers, finally gives a stick of light coherent metal, of increasing height, as illustrated at A in Fig. 2.

This stick is detached and the operation is repeated by bringing back the cathode F in contact with the bath.

According to the light metal to be extracted, the lower end of the copper cylinder F can be lined with another metal, iron, nickel, alloy, etc, which does not risk of melting or of soiling the metal produced.

When the alloy-anode is sufiiciently exhausted of lightmetal, the residual part is evacuated and a new batch of alloy to be treated is re-introduced in the vat, .or a new batch of light metal is re-incorporated on the spot with said residual part,-ifa refining operation is to be effected.

From the foregoing, it will be seen that th object and function of the rising cathode applied as stated, notably difl'er from what they are in the old known process.

, In fact, in this old process, the object sought for is to obtain a very high density of current for succeeding in releasing, in a compact condition, a metal from a salt the electrolysis of which is effected with difliculty.

In the present invention, the rising cathode is solely used for localizing the surface of the cathodic deposite in order to hold it at a suflicient'distance from the wall of the vat, that is to say for limiting the horizontal extension of the deposit of the light metal and thus preventing the metal, which collects on the cathode, from coming in contact with the wall of the vat.

In the present application of the rising cathode to the extraction of the metals which, as magnesium and aluminium, admit somewhat variable current densities, of the average order of 1 ampere per square centimeter, it is possible to give to this cathode a larger diameter than in the previous system for the case of calcium.

As auxiliary to this increase of diameter, a cooling of F and, if need be of H, can be effected by any suitable means, such for instance as by causing the cathode to pass in a cooled sheath which surrounds it, without hindering its movements.

' Ventilated gills and the like can be ar ranged on the cylinder F.

A modication which it has not been possible to carry out with the side and non metallic anode of the previous process, consists in arranging, on a vat, a number of rising cathodes operating in parallel on the same bath and opposite one and the same anode. A vat mode of grouping; it could be rectangular or oval for instance, and it could thus have prising dimensions and a capacity of production notably increased.

The invention further comprises means for obtaining, with the rising cathode, metal sticks having a shape much more regular than was usually heretofore possible.

This means consists in causing the cathode The foregoing specification of my Improvement in the electrolytic extraction of light metals contained in alloys; signed by me this thirtieth day of November 1928.

PAUL LEON HULIN.

to rotate about its axis at the same time that 7 it rises, that is to say, in imparting to this cathode a movement of rotation on itself in addition to its rising movement.

Bythe combination of these two simultaneous movements imparted to the cathode, more perfectly cylindrical deposits are obtained in all cases, without prejudicious protuberances as well as a more stable general operation which is better in every respect.

The speed of rotation is not rigorous and can notably vary. There is no need to increase the speed much beyond that which is shown to be sufiicient by a trial, in each case, this speed usually corresponding to a few revolutions per minute.

The mechanism necessary for this rotary movement added to the vertical movement with the accessories embodied in the Whole structure (friction contacts, driving members, etc.) are easy to devise and need not be described, as they can assume varied shapes and arrangements which do not form a part of the invention.

All the details for carrying out the invention may be varied according to circumstances without altering. the principle of the said invention.

I claim:

1. An apparatus for the electrolytic extraction by means of fusion of light metals comprising a vat, an anode of molten metal of an alloy of the metal to be extracted, an electrolyte and a rising cathode formed by the solidified extracted metal.

2. An apparatus for the electrolytic extraction by means of fusion of light metals comprising a vat, an anode of molten metal of an alloy of the metal to be extracted, an elec trolyte and a rising cathode formed b the solidified extracted metal, the cathode eing formed by multiple rods disposed in parallel opposite the single anode in a molten alloy.

3. An apparatus for the electrolytic extraction by means of fusion of light metals coma vat, an anode of molten metal of an alloy of the metal to be extracted, an electrolyte and a rising cathode formed by the solidified extracted metal, and means for imparting a movement of rotation to the rising cathode.

4. An apparatus for the electrolytic extraction by means of fusion of light metals comprlsinga vat, an anode of molten metal of an alloy of the metal to be extracted, an electrolyte and a rising cathode formed by the solidified extracted metal and a frame or lining of carbon on a level with the upper layer. 

